A well is extracting shale gas in Yibin, Southwest China's Sichuan Province. Photo: VCG

Geologists called for "permanent" environmental monitoring and addressing environmental concerns before industrial extraction of shale gas begins, after state oil giant Sinopec announced it discovered a reserve of 124.7 billion cubic meters of shale gas in Southwest China's Sichuan Province. 

The gas was discovered in Neijiang and Zigong in Sichuan. The company is expected to develop a gas field with an annual output of 1 billion cubic meters of gas by the end of the year, Science and Technology Daily (STD) reported Tuesday. 

Such a reserve could sustain a city of 1 million residents for more than 100 years, suggested media reports when a similar-sized reserve in the Bohai Sea off the coast of North China was announced on February 25. 

A newly drilled well in the Sichuan gas field, which is of 4,200 meters deep, has a gas flow of 310,000 cubic meters a day, demonstrating the reserve's rich extraction potential, STD reported.

Twelve wells have been completed and another 32 are being drilled in the exploration area.

Experts noted that China's shale gas extraction is in the initial phase with great potential as the country is adjusting its energy structure to achieve environmental protection goals. 

But shale gas exploration also raises concerns for the local ecological and the potential geological impact the extraction activities might have. 

Fu Bingjun, a research fellow with the Institute of Geology and Geophysics at Chinese Academy of Sciences, told the Global Times on Tuesday that such activities do have impact on vegetation and geological structures, and a potential risk of explosions. 

He called for comprehensive risk analysis and feasibility studies before starting any construction work.

Environmental monitoring is a permanent mission and the scope of the monitoring should be wider than the gas field itself as some impacts could be "indirect and far-reaching," said Fu.  

Shale gas extraction was halted in Rongxian country, Zigong, Sichuan Province in February after local residents complained that the exploitation was responsible for frequent earthquakes.

The shale gas-rich Sichuan Basin in Southwest China produced about one-third of the country's total shale gas in 2017, the Xinhua News Agency reported.